Design of Equangular Spiral Helix Antenna

International Journal of Recent Technology and Engineering (IJRTE) ISSN: 2277-3878, Volume-7, Issue-5S4, February 2019

Patri Upender, P. Nageswara Rao, K. R. Anudeep Laxmikanth

Abstract—This paper presents the design of Equiangular Where k is the radius of the spiral, ‘k’ is initial radius of Spiral Helix Antenna in the frequency range from 0.5-18 GHz  where the helical antenna is operating over the frequency range the spiral, If the angle is increased by one full turn, the of 0.5-2GHz and spiral antenna over the range of 2-18GHz to e−a achieve circularly polarized radiation for the same frequency radius vector is increased by the factor , hence each band. This Antenna gives frequency range turn of the spiral is identical with every other turn except for with unrealizable during a one device. VSWR, beam width, gain a constant multiplier [4]. is determined over the entire band of 0.5-18 GHz. Designing this antenna is critical due to compact size and broadband characteristics. Keywords—Helix Antenna, polarization, VSWR, beam width, gain, Spiral

I. INTRODUCTION In 1954 E.M Turner developed these spiral antennas. The spiral antenna is category of freelance antenna below Fig. 2. Two arm equiangular spiral antenna angular construct. Photo etching process is used for fabrication of spiral antenna on copper clad structure. II. DESIGN SPECIFICATIONS Circularly polarized waves in bidirectional beam will be A. Design of Equiangular Spiral generated by spiral antenna perpendicular to the plane. The geometry of the spiral can be obtained from the Frequency band of radiation is limited by the physical equation dimension of spiral [1]. To get unifacial beam, the spiral is a built at the open end of a closed R= r0 e , r0 is radius and a is growth rate back silver cavity, once within the region of λ /4 deep pre- The smallest and largest diameters are known by the directs this 1/2 the energy constructively to for one beam. lowest frequencies and highest. To avoid end effects, the However the energy among the cavity is absorbed to attain a diameters must be taken 10% greater that of theoretical broadband radiation. The spiral radiator, being a balanced results. device, should be fed from a balanced line. Spiral antenna • Lower frequency = 2 GHz consists of three main components [2]. They are: • Higher frequency = 18 GHz 1) The backing cavity 2) The spiral radiator 3) The balun • Outer diameter = 47.7 mm transformer • Actual diameter taken = 63mm • Inner diameter = 5.3mm B Balun Design Different types of written circuit’s baluns square measure on the market for connecting a 2 arm spiral antenna. Tchebychev transformation with printed circuit balun is optimum [6]. To design printed circuit broad band balun a computer program is developed. Balun consists of center conductor and ground plane, which are printed on either side

of substrate as shown figure 3 [7]. Fig.1. Archimedean spiral antenna The equiangular spiral is one geometrical configuration whose surface can be described by angles. The equiangular spiral is described by following equation [3]   = ke (1)

Revised Manuscript Received on December 22, 2018. Fig. 3. Balun showing ground plane and centre Patri Upender, Department of Electronics and Communication, Vignan Institute of Technology and Science, Hyderabad, India conductor P. Nageswara Rao, Department of Electronics and Communication, Vignan Institute of Technology and Science, Hyderabad, India K. R. Anudeep Laxmikanth, Department of Electronics and Communication, Vignan Institute of Technology and Science, Hyderabad, India

Published By: Blue Eyes Intelligence Engineering Retrieval Number: E10690275S419/19©BEIESP 324 & Sciences Publication

DESIGN OF EQUANGULAR SPIRAL HELIX ANTENNA

C. Cavity Design It was designed to suit the spiral card. The measurements square having specified the aspect of the cavity same to the biggest sq. aspect of the spiral. Antenna gain is going to be most once the depth of the cavity is λ/4. In fact, this cannot be attained over the full band of 0.5-18 GHz. Hence honeycomb absorber is used to load cavity to avoid interference of the reflected signal from the bottom of the cavity [8]. Depth of the cavity = λ/4 at lower frequency. D. Spiral antenna assembly This antenna is soldered using the feed points of the spiral [9]. Using naked eye feed connection cannot be achieved so it is very critical [10]. Using the microscope this was done. Fig. 6. Design of spiral antenna using HFSS The balun is loaded with absorbent material and also spacer discs. III. SIMULATUION RESULTS Figure 7 gives the radiation pattern of spiral helix antenna which at 2, 6, 8, 14 and 18GHz. From the figure, it has been observed that the beam width of 59.85, 50.67, 90.07, 95.57 and 95.64 is obtained for an antenna is and axial ratio obtained is 0 for 2, 6, 8 GHz and 0.1, 0.2 for 14 and 18 GHz.

Fig. 4. Assembly of Spiral Antenna A MATLAB program is developed for design of spiral circuit. The above data is given as input to the program developed. Spiral co-ordinates are obtained from the developed program which will be helpful in auto CAD design.

Diameter in nm in both axis Fig. 5. Design of spiral antenna using Matlab. The design specifications of helix are Pitch angle = 15o, Number of arms = 2, Arm width = 9mm, Spacing = 18mm, Height = 70mm, Diameter = 63mm, Arm length = 270mm. Fig. 7. Radiation pattern of spiral at 2, 6, 8, 14 and The design of spiral chord and balun are done using a 18GHz computer program generated in MATLAB software. With The antenna is measured over the frequency range of 0.5- the above specifications we designed a helical antenna using 18 GHZ. The maximum VSWR is to be 2.78 at 2 GHZ and HFSS software and results are checked after simulation. <3.33 at other frequencies After found the results are good enough we made a AUTOCAD drawing to sent it for fabrication.

Published By: Blue Eyes Intelligence Engineering Retrieval Number: E10690275S419/19©BEIESP 325 & Sciences Publication

International Journal of Recent Technology and Engineering (IJRTE) ISSN: 2277-3878, Volume-7, Issue-5S4, February 2019

Fig. 8. VSWR Plot for spiral antenna for 0.5-18 GHZ

Using HFSS simulation of Helical antenna is as shown Fig. 12. Practical helix spiral and spiral antenna Figure 12 shows the helix spiral and spiral antenna fabricated using Photolithographic Process. Figure 13 shows radiation pattern of spiral helix antenna at 0.5, 1, 2, 6, 10, 14, 18 GHz

Fig. 9. Design of helical antenna using HFSS

Fig. 10. VSWR plot helical antenna Figure 11 shows the design of Helix Spiral antenna using HFSS.

Fig.11. Design of helix spiral antenna using HFSS

IV. FABRICATION RESULTS The design parameters determine the whole dimensions of the spiral antenna. Coordinates are obtained using the software programs developed in MATLAB. The fabrication is done by photolithographic process. Spiral antenna characteristics greatly depend on the type of material used as dielectric substrate. Thin substrates with higher dielectric constants are desirable for microwave circuitry. Hence Fig. 13. Radiation pattern of spiral helix antennas at 0.5, copper clad substrate is used. For fabrication of the antenna 1, 2, 6, 10, 14, 18 GHz it involves in design, master drawing, artwork layout, photo reduction, positive development, laminate cleaning, resist application, resist exposure, resist development, inspection, etching, bonding and finishing. \

DESIGN OF EQUANGULAR SPIRAL HELIX ANTENNA

Table 1.Comparision of Simulated, Realized and Specified specifications Specifications Specified Simulated Realized Frequency 0.5-18GHz 0.5-18GHz 0.5-18GHz VSWR <3.5 <3.5 <2.5 50 (min), 40 (min), 60 (min), Beam width 75(nom), 80(nom), 75(nom), 110(max) 100(max) 110(max) Polarization Circular Circular Circular -21dB at -21dB at -18dB at Gain 0.5GHz 0.5GHz 0.5GHz Axial ratio 2dB 1.5dB 2dB

V. CONCLSUION Equiangular spiral Helix Antenna with frequency band between 0.5 - 18GHz is designed. Circular polarization is achieved over a wide bandwidth. VSWR of 2:1(max) in the band of 0.5-18 GHz is achieved and symmetric patterns are with beam width varying from 61º to 110º, the axial ratio is obtained as 2dB. Spiral helix antenna is designed by generating computer programs and different software’s. Theoretical calculations and design methodology under the frequency of is presented.

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